This invention relates to a novel pyrazolesulfonamide derivative, a process for preparing the compound and a herbicide cotaining the compounds as an active component. In order to protect important crops such as rice plants, wheat, cotton and sugar beets from damges by weeds to achieve an increased yield, it is indispensable to use a herbicide. In recent years in particular, a herbicide having selectivity (or discriminativity) is saught after as it can kill only weeds selectively (or discriminatively) without damages to crops by agricultural chemicals even when a foliage treatment is applied simultaneously on crops and weeds in a cultivated land wherein useful crops and weeds are grown together. Also, from viewpoints of the prevention of environmental pollution, the transportion, and the economical cost reduction in application of chemicals, studies and researches have been made over many years on such compounds that may achieve a higher herbicidal activity with use of chemcicals in a lower amount. Some of the compounds having such a property are presently used as the herbicide having selectivity. Still, however, there are further demands for new compounds having such a property.
Conventionally, a number of compounds having sulfonylurea structure has been known. Any of these, however, show very strong activities to sugar beets. For example, sugar beets have extremely high sensibility to chlorsulfuron which is known as a herbicide for wheat, and accordingly the sugar beets which are cultured as second crops of wheat are known to be seriously suffered from damages by agricultural chemicals even after two years, because of a trace amount of the acvtive component remaining in the soil. Also, other sulfonylurea compounds than the chlorsulfuron are also considered to have very particularly strong effect to sugar beets, and, of the sulfonylurea type compounds, the compound which may have the selectivity on sugar beets have been hitherto almost unknown.
As a prior technique, European Patent Publication No. 87,780 discloses a pyrazolesulfonylurea which may have the sturcture similar to the compound of this invention. However, there has been nothing disclosing the compound wherein a heterocyclic ring is substituted on a pyrazole ring as this invention discloses.